1. Field of the Invention
The present invention relates to a paper feeder for pulling out and sending papers from a bundle of papers loaded on a paper tray, and an image forming apparatus including this paper feeder.
2. Description of the Related Art
An example of this kind of paper feeders is disclosed in JP H6-1467 (hereinafter referred to as Patent Literature 1). Here, a paper transport belt is arranged above the paper tray, air is breathed from an air hole on the paper transport belt through an air intake duct towards a fan, and papers in a bundle of papers on the paper tray is attached to the paper transport belt and thus transported. The air exhausted by the same fan is blown through an exhaust duct against the sides of the bundle of papers on the paper tray, thus the air is caused to flow into the respective papers in the bundle of papers to reduce the adhesion between the papers, thereby facilitating pulling out of each paper. Both the air breathed and the air exhausted by a single fan are used to save the number of parts.
Further, a valve is provided to the air intake duct, and an air path in the air intake duct is narrowed by this valve, thereby adjusting the amount of air that flows in the air path in the air intake duct.
Incidentally, with the configuration where a single fan breaths air from the air hole on the paper transport belt through the air intake duct and causes air to blow through the exhaust duct against the sides of a bundle of papers on the paper tray, the amounts of air breathed by the fan and that exhausted by the fan are approximately the same, and one of the amounts of air decreases as the other decreases. Therefore, when a sheet of paper is attached to the paper transport belt and blocks the air hole on the paper transport belt and the amount of the breathed air decreases, the amount of the air blown against the sides of the bundle of papers on the paper tray accordingly decreases, the air is not caused to flow into the papers, the adhesion between the papers is not reduced, and a transportation error where a plurality of papers are simultaneously pulled out occurs in some cases.
Also in Patent Literature 1, the amount of air that flows in the air path in the air intake duct is adjusted by narrowing the air path in the air intake duct with the valve. However, if the air hole on the paper transport belt is blocked and the amount of the air breathed towards the air intake duct reduces, the amount of air is not increased even if the valve is opened.
The present invention was made in light of the foregoing conventional problems, and it is an object thereof to provide a paper feeder in which it is assumed a configuration where papers are attached to the paper transport belt and air is blown against the sides of a bundle of papers using the air breathed and exhausted with a single fan, and even if a sheet of paper is attached to the paper transport belt, the amount of air blown against the sides of the bundle of papers does not reduce, and an image forming apparatus including this paper feeder.